1. Field of the Invention
The present invention relates to an electronic device and a manufacturing method therefor.
2. Description of the Related Art
Recently there has been proposed a TSV (through-silicon-via) technology of providing a semiconductor substrate such as a silicon substrate with a large number of through-electrodes. With the TSV technology, many functions can be packed into a small footprint, and important electrical pathways between elements can also be dramatically shortened to facilitate increasing processing speed.
When using the TSV technology, the through-electrodes have to be electrically insulated from the silicon substrate. As means for electrical insulation, Japanese Unexamined Patent Application Publication No. 2008-251964 discloses a technology of forming a ring-shaped isolation groove passing through a silicon substrate in such a manner as to surround a through-electrode passing through the silicon substrate in a spaced apart relationship, forming a silicon film directly on the bottom face and the side faces of the isolation groove, then forming an insulation film on the silicon film in such a manner as to fill up a gap left in the isolation groove, and thermally oxidizing each face of the silicon film in contact with the inner or outer peripheral side face of the isolation groove into a thermally-oxidized silicon film.
However, since the distance between the through-electrodes has to be large in the structure where the ring-shaped, insulating isolation groove is provided to surround the through-electrode passing through the silicon substrate in a spaced apart relationship, there is a limit on high-density distribution of the through-electrodes and further increase in performance and functionality of the electronic device.
Moreover, since it requires the steps of forming a silicon film directly on the bottom face and the side faces of the isolation groove, forming an insulation film on the silicon film in such a manner as to fill up a gap left in the isolation groove after formation of the silicon film, and then thermally oxidizing the surface of the silicon film, the process inevitably becomes complicated and time-consuming. When replacing the conventional planar arrangement with the TSV technology, cost performance is important from the viewpoint of industrial mass production, but the above related art cannot meet this need sufficiently.
Furthermore, since the isolation groove has to be filled with a film in the above related art, the groove width of the isolation groove has to be set at an extremely small value, e.g., about 2 μm, so that considering the ordinary thickness of a wafer, the aspect ratio of the isolation groove becomes as large as 100 to 200. This makes it difficult to form a silicon film in the isolation groove.
Since electronic devices, to which the TSV technology is to be applied, need higher frequency from the viewpoint of increasing the processing speed and the transfer rate, it is required to suppress the leakage of high-frequency current passing through the through-electrode as much as possible, i.e., to improve the high-frequency characteristics.
The TSV technology is applicable to a wide variety of electronic devices having the semiconductor substrate as a functional element, such as a sensor module, an optoelectronic module, a unipolar transistor, a MOS FET, a CMOS FET, a memory cell, integrated circuits (IC) thereof, various scales of LSIs, a light-emitting diode, and a solar cell, but the above-described problems occur in any case. It should be noted that related art documents also include Japanese Unexamined Patent Application Publication Nos. 2000-311982, 2004-095849, 2009-277927, 2006-024653, 2006-049557, 10-215044 and 2008-47895.